Elderly women regulate brain blood flow better than men do

Brain-body mechanisms contribute to sexual dimorphism in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most common form of human motor neuron disease. It is characterized by the progressive degeneration of upper and lower motor neurons, leading to generalized motor weakness and, ultimately, respiratory paralysis and death within 3-5 years. The disease is shaped by genetics, age, sex and environmental stressors, but no cure or routine biomarkers exist for the disease. Male individuals have a higher propensity to develop ALS, and a different manifestation of the disease phenotype, than female individuals. However, the mechanisms underlying these sex differences remain a mystery. In this Review, we summarize the epidemiology of ALS, examine the sexually dimorphic presentation of the disease and highlight the genetic variants and molecular pathways that might contribute to sex differences in humans and animal models of ALS. We advance the idea that sexual dimorphism in ALS arises from the interactions between the CNS and peripheral organs, involving vascular, metabolic, endocrine, musculoskeletal and immune systems, which are strikingly different between male and female individuals. Finally, we review the response to treatments in ALS and discuss the potential to implement future personalized therapeutic strategies for the disease.

Cerebrovascular responses to a 90° tilt in healthy neonates

BACKGROUND

Tilts can induce alterations in cerebral hemodynamics in healthy neonates, but prior studies have only examined systemic parameters or used small tilt angles (<90°). The healthy neonatal population, however, are commonly subjected to large tilt angles (≥90°). We sought to characterize the cerebrovascular response to a 90° tilt in healthy term neonates.

METHODS

We performed a secondary descriptive analysis on 44 healthy term neonates. We measured cerebral oxygen saturation (rcSO2), oxygen saturation (SpO2), heart rate (HR), breathing rate (BR), and cerebral fractional tissue oxygen extraction (cFTOE) over three consecutive 90° tilts. These parameters were measured for 2-min while neonates were in a supine (0°) position and 2-min while tilted to a sitting (90°) position. We measured oscillometric mean blood pressure (MBP) at the start of each tilt.

RESULTS

rcSO2 and BR decreased significantly in the sitting position, whereas cFTOE, SpO2, and MBP increased significantly in the sitting position. We detected a significant position-by-time interaction for all physiological parameters.

CONCLUSION

A 90° tilt induces a decline in rcSO2 and an increase in cFTOE in healthy term neonates. Understanding the normal cerebrovascular response to a 90° tilt in healthy neonates will help clinicians to recognize abnormal responses in high-risk infant populations.

IMPACT

Healthy term neonates (≤14 days old) had decreased cerebral oxygen saturation (~1.1%) and increased cerebral oxygen extraction (~0.01) following a 90° tilt. We detected a significant position-by-time interaction with all physiological parameters measured, suggesting the effect of position varied across consecutive tilts. No prior study has characterized the cerebral oxygen saturation response to a 90° tilt in healthy term neonates.

The effect of hypercapnia on the directional sensitivity of dynamic cerebral autoregulation and the influence of age and sex

The cerebral circulation responds differently to increases in mean arterial pressure (MAP), compared to reductions in MAP. We tested the hypothesis that this directional sensitivity is reduced by hypercapnia. Retrospective analysis of 104 healthy subjects (46 male (44%), age range 19-74 years), with five minute recordings of middle cerebral blood velocity (MCAv, transcranial Doppler), non-invasive MAP (Finometer) and end-tidal CO2 (capnography) at rest, during both poikilocapnia and hypercapnia (5% CO2 breathing in air) produced MCAv step responses allowing estimation of the classical Autoregulation Index (ARIORIG), and corresponding values for both positive (ARI+D) and negative (ARI-D) changes in MAP. Hypercapnia led to marked reductions in ARIORIG, ARI+D and ARI-D (p < 0.0001, all cases). Females had a lower value of ARIORIG compared to males (p = 0.030) at poikilocapnia (4.44 ± 1.74 vs 4.74 ± 1.48) and hypercapnia (2.44 ± 1.93 vs 3.33 ± 1.61). The strength of directional sensitivity (ARI+D-ARI-D) was not influenced by hypercapnia (p = 0.46), sex (p = 0.76) or age (p = 0.61). During poikilocapnia, ARI+D decreased with age in females (p = 0.027), but not in males. Directional sensitivity was not affected by hypercapnia, suggesting that its origins are more likely to be inherent to the mechanics of vascular smooth muscle than to myogenic pathways.

Influence of end-tidal CO2 on cerebral blood flow during orthostatic stress in controls and adults with myalgic encephalomyelitis/chronic fatigue syndrome

Brain perfusion is sensitive to changes in CO2 levels (CO2 reactivity). Previously, we showed a pathological cerebral blood flow (CBF) reduction in the majority of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) patients during orthostatic stress. Limited data are available on the relation between CO2 and CBF changes in ME/CFS patients. Therefore, we studied this relation between ME/CFS patients and healthy controls (HC) during tilt testing. In this retrospective study, supine and end-tilt CBF, as measured by extracranial Doppler flow, were compared with PET CO2 data in female patients either with a normal heart rate and blood pressure (HR/BP) response or with postural orthostatic tachycardia syndrome (POTS), and in HC. Five hundred thirty-five female ME/CFS patients and 34 HC were included. Both in supine position and at end-tilt, there was a significant relation between CBF and PET CO2 in patients (p < 0.0001), without differences between patients with a normal HR/BP response and with POTS. The relations between the %CBF change and the PET CO2 reduction were both significant in patients and HC (p < 0.0001 and p = 0.0012, respectively). In a multiple regression analysis, the patient/HC status and PET CO2 predicted CBF. The contribution of the PET CO2 to CBF changes was limited, with low adjusted R2 values. In female ME/CFS patients, CO2 reactivity, as measured during orthostatic stress testing, is similar to that of HC and is independent of the type of hemodynamic abnormality. However, the influence of CO2 changes on CBF changes is modest in female ME/CFS patients.

The utility of therapeutic hypothermia on cerebral autoregulation

Cerebral autoregulation (CA) dysfunction is a strong predictor of clinical outcome in patients with acute brain injury (ABI). CA dysfunction is a potential pathologic defect that may lead to secondary injury and worse functional outcomes. Early therapeutic hypothermia (TH) in patients with ABI is controversial. Many factors, including patient selection, timing, treatment depth, duration, and rewarming strategy, impact its clinical efficacy. Therefore, optimizing the benefit of TH is an important issue. This paper reviews the state of current research on the impact of TH on CA function, which may provide the basis and direction for CA-oriented target temperature management.

Association of Cerebrovascular Stability Index and Head Circumference Between Infants With and Without Congenital Heart Disease

Congenital heart disease (CHD) is a common birth defect in the United States. CHD infants are more likely to have smaller head circumference and neurodevelopmental delays; however, the cause is unknown. Altered cerebrovascular hemodynamics may contribute to neurologic abnormalities, such as smaller head circumference, thus we created a novel Cerebrovascular Stability Index (CSI), as a surrogate for cerebral autoregulation. We hypothesized that CHD infants would have an association between CSI and head circumference. We performed a prospective, longitudinal study in CHD infants and healthy controls. We measured CSI and head circumference at 4 time points (newborn, 3, 6, 9 months). We calculated CSI by subtracting the average 2-min sitting from supine cerebral oxygenation (rcSO₂) over three consecutive tilts (0-90°), then averaged the change score for each age. Linear regressions quantified the relationship between CSI and head circumference. We performed 177 assessments in total (80 healthy controls, 97 CHD infants). The average head circumference was smaller in CHD infants (39.2 cm) compared to healthy controls (41.6 cm) (p < 0.001) and head circumference increased by 0.27 cm as CSI improved in the sample (p = 0.04) overall when combining all time points. Similarly, head circumference increased by 0.32 cm as CSI improved among CHD infants (p = 0.04). We found CSI significantly associated with head circumference in our sample overall and CHD infants alone, which suggests that impaired CSI may affect brain size in CHD infants. Future studies are needed to better understand the mechanism of interaction between CSI and brain growth.

Higher body mass index is associated with worse hippocampal vasoreactivity to carbon dioxide

Background and objectives

Obesity is a risk factor for cognitive decline. Probable mechanisms involve inflammation and cerebrovascular dysfunction, leading to diminished cerebral blood flow (CBF) and cerebrovascular reactivity (CVR). The hippocampus, crucially involved in memory processing and thus relevant to many types of dementia, poses a challenge in studies of perfusion and CVR, due to its location, small size, and complex shape. We examined the relationships between body mass index (BMI) and hippocampal resting CBF and CVR to carbon dioxide (CVRCO2) in a group of cognitively normal middle-aged and older adults.

Methods

Our study was a retrospective analysis of prospectively collected data. Subjects were enrolled for studies assessing the role of hippocampal hemodynamics as a biomarker for AD among cognitively healthy elderly individuals (age > 50). Participants without cognitive impairment, stroke, and active substance abuse were recruited between January 2008 and November 2017 at the NYU Grossman School of Medicine, former Center for Brain Health. All subjects underwent medical, psychiatric, and neurological assessments, blood tests, and MRI examinations. To estimate CVR, we increased their carbon dioxide levels using a rebreathing protocol. Relationships between BMI and brain measures were tested using linear regression.

Results

Our group (n = 331) consisted of 60.4% women (age 68.8 ± 7.5 years; education 16.8 ± 2.2 years) and 39.6% men (age 70.4 ± 6.4 years; education 16.9 ± 2.4 years). Approximately 22% of them (n = 73) were obese. BMI was inversely associated with CVRCO2 (β = -0.12, unstandardized B = -0.06, 95% CI -0.11, -0.004). A similar relationship was observed after excluding subjects with diabetes and insulin resistance (β = -0.15, unstandardized B = -0.08, 95% CI -0.16, -0.000). In the entire group, BMI was more strongly related to hippocampal CVRCO2 in women (β = -0.20, unstandardized B = -0.08, 95% CI -0.13, -0.02).

Discussion

These findings lend support to the notion that obesity is a risk factor for hippocampal hemodynamic impairment and suggest targeting obesity as an important prevention strategy. Prospective studies assessing the effects of weight loss on brain hemodynamic measures and inflammation are warranted.

Variation in Mean Arterial Pressure Increases Falls Risk in Elderly Physically Frail and Prefrail Individuals Treated With Antihypertensive Medication

BACKGROUND

Impaired cerebral blood flow has been associated with an increased risk of falls. Mean arterial pressure (MAP) and variability in MAP have been reported to affect cerebral blood flow but their relationships to the risk of falls have not previously been reported.

METHODS

Utilising data from the Aspirin in Reducing Events in the Elderly trial participants, we estimated MAP and variability in MAP, defined as within-individual SD of MAP from baseline and first 2 annual visits. The relationship with MAP was studied in 16 703 participants amongst whom 1539 falls were recorded over 7.3 years. Variability in MAP was studied in 14 818 of these participants who experienced 974 falls over 4.1 years. Falls were confined to those involving hospital presentation. Cox regression was used to calculate hazard ratio and 95% CI for associations with falls.

RESULTS

Long-term variability in MAP was not associated with falls except amongst frail or prefrail participants using antihypertensive medications. Within this group each 5 mm Hg increase in long-term variability in MAP increased the risk of falls by 16% (hazard ratio, 1.16 [95% CI, 1.02-1.33]). Amongst the antihypertensive drugs studied, beta-blocker monotherapy (hazard ratio, 1.93 [95% CI, 1.17-3.18]) was associated with an increased risk of falls compared with calcium channel blockers.

CONCLUSIONS

Higher levels of long-term variability in MAP increase the risk of serious falls in older frail and prefrail individuals taking antihypertensive medications. The observation that the relationship was limited to frail and prefrail individuals might explain some of the variability of previous studies linking blood pressure indices and falls.

Age and sex related differences in orthostatic cerebral oxygenation: Findings from 2764 older adults in the Irish Longitudinal Study on Ageing (TILDA)

AIMS

Cerebral hypoperfusion is implicated in the pathogenesis of associations between orthostatic hypotension and adverse outcome such as falls, cognitive impairment, depression, and mortality. Although the blood pressure response to orthostasis has been well studied there is a lack of information on orthostatic cerebrovascular responses in older populations.

METHODS AND RESULTS

We measured cerebral hemodynamics, utilizing near infrared spectroscopy, coupled with peripheral blood pressure during an active stand in a large population of well-phenotyped older adults (N = 2764). Multi-level mixed effect models were utilized to investigate associations with age and sex, as well as confounders including anti-hypertensive medications. Normative cerebral oxygenation responses were also modelled utilizing generalized additive models for location, scale, and shape (GAMLSS). Older age groups experienced larger initial drops in oxygenation and a slower recovery, and responses also differed by sex. The drop after standing ranged from -1.85 % (CI: -2.02 to -1.68) in the males aged 54-59 years vs -1.15 % (CI: -1.31 to -1.00 %) in females aged 54-59 years, to -2.67 % (CI: -3.01 to -2.33) in males aged ≥ 80 years vs -1.97 % (CI: -2.32 to -1.62) females aged ≥ 80 years. Reduced oxygenation levels were also evident in those taking anti-hypertensive medications.

CONCLUSION

Cerebral autoregulation is impaired with age, particularly in older women and those taking anti-hypertensives. SBP during the stand explained some of the age gradient in the late recovery stage of the stand for the oldest age group. Reported orthostatic symptoms did not correlate with hypoperfusion. Therefore, measures of orthostatic cerebral flow should be assessed in addition to peripheral BP in older patients irrespective of symptoms. Further studies are required to investigate the relationship between NIRS measurements and clinical outcomes such as falls, cognitive impairment and depression.

Variation within the visually evoked neurovascular coupling response of the posterior cerebral artery is not influenced by age or sex

Neurovascular coupling (NVC) is the temporal and spatial coordination between local neuronal activity and regional cerebral blood flow. The literature is unsettled on whether age and/or sex affect NVC, which may relate to differences in methodology and the quantification of NVC in small sample-sized studies. The aim of this study was to 1) determine the relative and combined contribution of age and sex to the variation observed across several distinct NVC metrics (n = 125, 21–66 yr; 41 males) and 2) present an approach for the comprehensive systematic assessment of the NVC response using transcranial Doppler ultrasound. NVC was measured as the relative change from baseline (absolute and percent change) assessing peak, mean, and total area under the curve (tAUC) of cerebral blood velocity through the posterior cerebral artery (PCAv) during intermittent photic stimulation. In addition, the NVC waveform was compartmentalized into distinct regions, acute (0–9 s), mid (10–19 s), and late (20–30 s), following the onset of photic stimulation. Hierarchical multiple regression modeling was used to determine the extent of variation within each NVC metric attributable to demographic differences in age and sex. After controlling for differences in baseline PCAv, the R² data suggest that 1.6%, 6.1%, 1.1%, 3.4%, 2.5%, and 4.2% of the variance observed within mean, peak, tAUC, acute, mid, and late response magnitude is attributable to the combination of age and sex. Our study reveals that variability in NVC response magnitude is independent of age and sex in healthy human participants, aged 21–66 yr.

NEW & NOTEWORTHY We assessed the variability within the neurovascular coupling response attributable to age and sex (n = 125, 21–66 yr; 41 male). Based on the assessment of posterior cerebral artery responses to visual stimulation, 0%–6% of the variance observed within several metrics of NVC response magnitude are attributable to the combination of age and sex. Therefore, observed differences between age groups and/or sexes are likely a result of other physiological factors.

Subclinical cognitive deficits are associated with reduced cerebrovascular response to visual stimulation in mid-sixties men

Reduced cerebrovascular response to neuronal activation is observed in patients with neurodegenerative disease. In the present study, we examined the correlation between reduced cerebrovascular response to visual activation (ΔCBF_Vis.Act) and subclinical cognitive deficits in a human population of mid-sixties individuals without neurodegenerative disease. Such a correlation would suggest that impaired cerebrovascular function occurs before overt neurodegenerative disease. A total of 187 subjects (age 64-67 years) of the Metropolit Danish Male Birth Cohort participated in the study. ΔCBF_Vis.Act was measured using arterial spin labelling (ASL) MRI. ΔCBF_Vis.Act correlated positively with cognitive performance in: Global cognition (p = 0.046), paired associative memory (p = 0.025), spatial recognition (p = 0.026), planning (p = 0.016), simple processing speed (p < 0.01), and with highly significant correlations with current intelligence (p < 10^-5), and more complex processing speed (p < 10^-3), the latter two explaining approximately 11-13% of the variance. Reduced ΔCBF_Vis.Act was independent of brain atrophy. Our findings suggest that inhibited cerebrovascular response to neuronal activation is an early deficit in the ageing brain and associated with subclinical cognitive deficits. Cerebrovascular dysfunction could be an early sign of a trajectory pointing towards the development of neurodegenerative disease. Future efforts should elucidate if maintenance of a healthy cerebrovascular function can protect against the development of dementia.

Females Exhibit Better Cerebral Pressure Autoregulation, Less Mitochondrial Dysfunction, and Reduced Excitotoxicity following Severe Traumatic Brain Injury

The aim of the study was to investigate sex-related differences in intracranial pressure (ICP) dynamics, cerebral pressure autoregulation (PRx55-15), cerebral energy metabolism, and clinical outcome after severe traumatic brain injury (TBI). One-hundred sixty-nine adult TBI patients, treated at the neurointensive care (NIC) unit, at Uppsala University Hospital, 2008-2020, with ICP and cerebral microdialysis (MD) monitoring, were included. Of the 169 TBI patients, 131 (78%) were male and 38 (22%) female. Male patients were more often injured by motor vehicle accidents and less often by bicycle accidents (p < 0.05). There were otherwise no difference in age, neurological status at admission, and types of intracranial hemorrhages between the sexes. The percent of monitoring time with ICP above 20 mmHg and CPP below 60 mmHg were similar for both sexes. Males exhibited more disturbed cerebral pressure autoregulation (PRx55-15 (mean ± SD); 0.28 ± 0.18 vs. 0.17 ± 0.23, p < 0.05) day 1, worse cerebral energy metabolism (MD-lactate-/pyruvate-ratio (median (IQR)); 25 (19-31) vs. 20 (17-25), p < 0.01) and mitochondrial dysfunction (higher burden of MD-LPR > 25 and MD-pyruvate > 120 µM (median (IQR)); 13 (0-58) % vs. 3 (0-17) %, p < 0.05) day 2 to 5, increased excitotoxicity (MD-glutamate median (IQR); 9 (4-32) µM vs. 5 (3-10) µM, p < 0.05) day 2 to 5, and higher biomarker levels of cellular injury (MD-glycerol median (IQR); 103 (66-193) µM vs. 68 (49-106) µM, p < 0.01) most pronounced day 6 to 10. There was no difference in mortality or the degree of favorable outcome between the sexes. Altogether, females exhibited more favorable cerebral physiology post-TBI, particularly better mitochondrial function and reduced excitotoxicity, but this did not translate into better clinical outcome compared to males. Future studies needs to further explore potential sex differences in secondary injury mechanisms in TBI.

Increased multimorbidity is associated with impaired cerebral and peripheral hemodynamic stabilization during active standing

Background

Age‐related morbidities and frailty are associated with impaired blood pressure (BP) and heart rate (HR) recovery after standing. Here we investigate how multimorbidity affects cerebral and peripheral hemodynamics during standing in a large sample of older patients.

Methods

Patients were recruited from a national Falls and Syncope Unit. They underwent an active stand test (5–10 min lying +3 min standing) with monitoring of continuous BP, HR, total peripheral resistance (TPR), stroke volume (SV), and a near‐infrared spectroscopy (NIRS) derived cerebral tissue saturation index (TSI). A multimorbidity count was derived from a 26‐item list of conditions. Features derived from the signals included: nadir, overshoot, value at 30 s, steady‐state and recovery rate. Robust linear regression was used to assess the association between multimorbidity, TSI and peripheral hemodynamics while correcting for covariates. A p‐value <0.05 was considered statistically significant.

Results

Multimorbidity was associated with poorer recovery of TSI at 30 s after standing (β: −0.15, CI:[−0.25–0.06], p = 0.009) independent of all peripheral hemodynamics. Impaired diastolic BP (DBP) recovery at 30s (β:−1.34, CI:[−2.29–0.40], p = 0.032), DBP steady‐state (β:−1.18, CI:[−2.04–0.32], p = 0.032), TPR overshoot‐to‐nadir difference (β:−0.041, CI:[−0.070–0.013], p = 0.045), and SV at 30s (β:1.30, CI:[0.45 2.15], p = 0.027) were also associated with increasing multimorbidity. After sex stratification, only females demonstrated impaired TSI with multimorbidity at overshoot (β: −0.19, CI: [−0.32 ‐0.07], p = 0.009), 30 s (β: −0.22 [−0.35–0.10], p = 0.005) and steady‐state (β: −0.20, CI:[−0.35–0.04], p = 0.023), independent of peripheral hemodynamics.

Conclusions

Transient cerebral oxygenation and peripheral hemodynamic responses are impaired with multimorbidity (frailty) in older patients, particularly in females. This study demonstrates the feasibility of using NIRS in this clinical context and may inform the development of clinical management strategies targeting both cerebral oxygenation and blood pressure impairments in patients with faints and falls.

The impact of age, sex, cardio-respiratory fitness, and cardiovascular disease risk on dynamic cerebral autoregulation and baroreflex sensitivity

Background

Humans display an age-related decline in cerebral blood flow and increase in blood pressure (BP), but changes in the underlying control mechanisms across the lifespan are less well understood. We aimed to; (1) examine the impact of age, sex, cardiovascular disease (CVD) risk, and cardio-respiratory fitness on dynamic cerebral autoregulation and cardiac baroreflex sensitivity, and (2) explore the relationships between dynamic cerebral autoregulation (dCA) and cardiac baroreflex sensitivity (cBRS).

Methods

206 participants aged 18–70 years were stratified into age categories. Cerebral blood flow velocity was measured using transcranial Doppler ultrasound. Repeated squat-stand manoeuvres were performed (0.10 Hz), and transfer function analysis was used to assess dCA and cBRS. Multivariable linear regression was used to examine the influence of age, sex, CVD risk, and cardio-respiratory fitness on dCA and cBRS. Linear models determined the relationship between dCA and cBRS.

Results

Age, sex, CVD risk, and cardio-respiratory fitness did not impact dCA normalised gain, phase, or coherence with minimal change in all models (P > 0.05). cBRS gain was attenuated with age when adjusted for sex and CVD risk (young–older; β = − 2.86 P < 0.001) along with cBRS phase (young–older; β = − 0.44, P < 0.001). There was no correlation between dCA normalised gain and phase with either parameter of cBRS.

Conclusion

Ageing was associated with a decreased cBRS, but dCA appears to remain unchanged. Additionally, our data suggest that sex, CVD risk, and cardio-respiratory fitness have little effect.

Sex differences in the blood-brain barrier: Implications for mental health

Prevalence of mental disorders, including major depressive disorder (MDD), bipolar disorder (BD) and schizophrenia (SZ) are increasing at alarming rates in our societies. Growing evidence points toward major sex differences in these conditions, and high rates of treatment resistance support the need to consider novel biological mechanisms outside of neuronal function to gain mechanistic insights that could lead to innovative therapies. Blood-brain barrier alterations have been reported in MDD, BD and SZ. Here, we provide an overview of sex-specific immune, endocrine, vascular and transcriptional-mediated changes that could affect neurovascular integrity and possibly contribute to the pathogenesis of mental disorders. We also identify pitfalls in current literature and highlight promising vascular biomarkers. Better understanding of how these adaptations can contribute to mental health status is essential not only in the context of MDD, BD and SZ but also cardiovascular diseases and stroke which are associated with higher prevalence of these conditions.

Machine Learning Models and Statistical Complexity to Analyze the Effects of Posture on Cerebral Hemodynamics

The mechanism of cerebral blood flow autoregulation can be of great importance in diagnosing and controlling a diversity of cerebrovascular pathologies such as vascular dementia, brain injury, and neurodegenerative diseases. To assess it, there are several methods that use changing postures, such as sit-stand or squat-stand maneuvers. However, the evaluation of the dynamic cerebral blood flow autoregulation (dCA) in these postures has not been adequately studied using more complex models, such as non-linear ones. Moreover, dCA can be considered part of a more complex mechanism called cerebral hemodynamics, where others (CO2 reactivity and neurovascular-coupling) that affect cerebral blood flow (BF) are included. In this work, we analyzed postural influences using non-linear machine learning models of dCA and studied characteristics of cerebral hemodynamics under statistical complexity using eighteen young adult subjects, aged 27 ± 6.29 years, who took the systemic or arterial blood pressure (BP) and cerebral blood flow velocity (BFV) for five minutes in three different postures: stand, sit, and lay. With models of a Support Vector Machine (SVM) through time, we used an AutoRegulatory Index (ARI) to compare the dCA in different postures. Using wavelet entropy, we estimated the statistical complexity of BFV for three postures. Repeated measures ANOVA showed that only the complexity of lay-sit had significant differences.

Reproducibility and diurnal variation of the directional sensitivity of the cerebral pressure-flow relationship in men and women

The cerebral pressure-flow relationship has directional sensitivity, meaning the augmentation in cerebral blood flow is attenuated when mean arterial pressure (MAP) increases vs MAP decreases. We employed repeated squat-stands (RSS) to quantify it using a novel metric. However, its within-day reproducibility and the impacts of diurnal variation and biological sex are unknown. Study aims were to evaluate this metric for: 1) within-day reproducibility and diurnal variation in middle (MCA; ∆MCAv_T/∆MAP_T) and posterior cerebral arteries (PCA; ∆PCAv_T/∆MAP_T); 2) sex differences. ∆MCAv_T/∆MAP_T and ∆PCAv_T/∆MAP_T were calculated at seven time-points (08:00-17:00) in 18 participants (8 women; 24 ± 3 yrs) using the minimum-to-maximum MCAv or PCAv and MAP for each RSS at 0.05 Hz and 0.10 Hz. Relative metric values were also calculated (%MCAv_T/%MAP_T, %PCAv_T/%MAP_T). Intraclass correlation coefficient (ICC) evaluated reproducibility, which was good (0.75-0.90) to excellent (>0.90). Time-of-day impacted ∆MCAv_T/∆MAP_T (0.05 Hz: p = 0.002; 0.10 Hz: p = 0.001), %MCAv_T/%MAP_T (0.05 Hz: p = 0.035; 0.10 Hz: p = 0.009), and ∆PCAv_T/∆MAP_T (0.05 Hz: p = 0.024), albeit with small/negligible effect sizes. MAP direction impacted both arteries' metric at 0.10 Hz (all p < 0.024). Sex differences in the MCA only (p = 0.003) vanished when reported in relative terms. These findings demonstrate this metric is reproducible throughout the day in the MCA and PCA and is not impacted by biological sex.

Transcriptome analysis reveals sexual disparities in gene expression in rat brain microvessels

Sex is an important determinant of brain microvessels (MVs) function and susceptibility to cerebrovascular and neurological diseases, but underlying mechanisms are unclear. Using high throughput RNA sequencing analysis, we examined differentially expressed (DE) genes in brain MVs from young, male, and female rats. Bioinformatics analysis of the 23,786 identified genes indicates that 298 (1.2%) genes were DE using False Discovery Rate criteria (FDR; p < 0.05), of which 119 (40%) and 179 (60%) genes were abundantly expressed in male and female MVs, respectively. Nucleic acid binding, enzyme modulator, and transcription factor were the top three DE genes, which were more highly expressed in male than female MVs. Synthesis of glycosylphosphatidylinositol (GPI), biosynthesis of GPI-anchored proteins, steroid and cholesterol synthesis, were the top three significantly enriched canonical pathways in male MVs. In contrast, respiratory chain, ribosome, and 3 ́-UTR-mediated translational regulation were the top three enriched canonical pathways in female MVs. Different gene functions of MVs were validated by proteomic analysis and western blotting. Our novel findings reveal major sex disparities in gene expression and canonical pathways of MVs and these differences provide a foundation to study the underlying mechanisms and consequences of sex-dependent differences in cerebrovascular and other neurological diseases.

Cerebral critical closing pressure and resistance-area product: the influence of dynamic cerebral autoregulation, age and sex

Instantaneous arterial pressure-flow (or velocity) relationships indicate the existence of a cerebral critical closing pressure (CrCP), with the slope of the relationship expressed by the resistance-area product (RAP). In 194 healthy subjects (20-82 years, 90 female), cerebral blood flow velocity (CBFV, transcranial Doppler), arterial blood pressure (BP, Finapres) and end-tidal CO2 (EtCO2, capnography) were measured continuously for five minutes during spontaneous fluctuations of BP at rest. The dynamic cerebral autoregulation (CA) index (ARI) was extracted with transfer function analysis from the CBFV step response to the BP input and step responses were also obtained for the BP-CrCP and BP-RAP relationships. ARI was shown to decrease with age at a rate of -0.025 units/year in men (p = 0.022), but not in women (p = 0.40). The temporal patterns of the BP-CBFV, BP-CrCP and BP-RAP step responses were strongly influenced by the ARI (p < 0.0001), but not by sex. Age was also a significant determinant of the peak of the CBFV step response and the tail of the RAP response. Whilst the RAP step response pattern is consistent with a myogenic mechanism controlling dynamic CA, further work is needed to explore the potential association of the CrCP step response with the flow-mediated component of autoregulation.

Sex differences in the association between major cardiovascular risk factors in midlife and dementia: a cohort study using data from the UK Biobank

BACKGROUND

Sex differences in major cardiovascular risk factors for incident (fatal or non-fatal) all-cause dementia were assessed in the UK Biobank. The effects of these risk factors on all-cause dementia were explored by age and socioeconomic status (SES).

METHODS

Cox proportional hazards models were used to estimate hazard ratios (HRs) and women-to-men ratio of HRs (RHR) with 95% confidence intervals (CIs) for systolic blood pressure (SBP) and diastolic blood pressure (DBP), smoking, diabetes, adiposity, stroke, SES and lipids with dementia. Poisson regression was used to estimate the sex-specific incidence rate of dementia for these risk factors.

RESULTS

502,226 individuals in midlife (54.4% women, mean age 56.5 years) with no prevalent dementia were included in the analyses. Over 11.8 years (median), 4068 participants (45.9% women) developed dementia. The crude incidence rates were 5.88 [95% CI 5.62-6.16] for women and 8.42 [8.07-8.78] for men, per 10,000 person-years. Sex was associated with the risk of dementia, where the risk was lower in women than men (HR = 0.83 [0.77-0.89]). Current smoking, diabetes, high adiposity, prior stroke and low SES were associated with a greater risk of dementia, similarly in women and men. The relationship between blood pressure (BP) and dementia was U-shaped in men but had a dose-response relationship in women: the HR for SBP per 20 mmHg was 1.08 [1.02-1.13] in women and 0.98 [0.93-1.03] in men. This sex difference was not affected by the use of antihypertensive medication at baseline. The sex difference in the effect of raised BP was consistent for dementia subtypes (vascular dementia and Alzheimer's disease).

CONCLUSIONS

Several mid-life cardiovascular risk factors were associated with dementia similarly in women and men, but not raised BP. Future bespoke BP-lowering trials are necessary to understand its role in restricting cognitive decline and to clarify any sex difference.

Cerebral oxygen saturation and cerebrovascular instability in newborn infants with congenital heart disease compared to healthy controls

Objective

Infants with Congenital Heart Disease (CHD) are at risk for developmental delays, though the mechanisms of brain injury that impair development are unknown. Potential causes could include cerebral hypoxia and cerebrovascular instability. We hypothesized that we would detect significantly reduced cerebral oxygen saturation and greater cerebrovascular instability in CHD infants compared to the healthy controls.

Methods

We performed a secondary analysis on a sample of 43 term infants (28 CHD, 15 healthy controls) that assessed prospectively in temporal cross-section before or at 12 days of age. CHD infants were assessed prior to open-heart surgery. Cerebral oxygen saturation levels were estimated using Near-Infrared Spectroscopy, and cerebrovascular stability was assessed with the response of cerebral oxygen saturation after a postural change (supine to sitting).

Results

Cerebral oxygen saturation was 9 points lower in CHD than control infants in both postures (β = -9.3; 95%CI = -17.68, -1.00; p = 0.028), even after controlling for differences in peripheral oxygen saturation. Cerebrovascular stability was significantly impaired in CHD compared to healthy infants (β = -2.4; 95%CI = -4.12, -.61; p = 0.008), and in CHD infants with single ventricle compared with biventricular defects (β = -1.5; 95%CI = -2.95, -0.05; p = 0.04).

Conclusion

CHD infants had cerebral hypoxia and decreased cerebral oxygen saturation values following a postural change, suggesting cerebrovascular instability. Future longitudinal studies should assess the associations of cerebral hypoxia and cerebrovascular instability with long-term neurodevelopmental outcomes in CHD infants.

Effect of menopause on cerebral artery blood flow velocity and cerebrovascular reactivity: Systematic review and meta-analysis

BACKGROUND

Menopause and its associated decline in oestrogen is linked to chronic conditions like cardiovascular disease and osteoporosis, which may be difficult to disentangle from the effects of ageing. Further, post-menopausal women are at increased risk of cerebrovascular disease, linked to declines in cerebral blood flow (CBF) and cerebrovascular reactivity (CVR), yet the direct understanding of the impact of the menopause on cerebrovascular function is unclear. The aim of this systematic review and meta-analysis was to examine the literature investigating CBF and CVR in pre- compared with post-menopausal women METHODS: Five databases were searched for studies assessing CBF or CVR in pre- and post-menopausal women. Meta-analysis examined the effect of menopausal status on middle cerebral artery velocity (MCAv), and GRADE-assessed evidence certainty RESULTS: Nine studies (n=504) included cerebrovascular outcomes. Six studies (n=239) reported negligible differences in MCAv between pre- and post-menopausal women [2.11cm/s (95% CI: -8.94 to 4.73, p=0.54)], but with a "low" certainty of evidence. MCAv was lower in post-menopausal women in two studies, when MCAv was adjusted for blood pressure. CVR was lower in post- compared with pre-menopausal women in two of three studies, but high-quality evidence is lacking. Across outcomes, study methodology and reporting criteria for menopause were inconsistent CONCLUSIONS: MCAv was similar in post- compared with pre-menopausal women. Methodological differences in characterising menopause and inconsistent reporting of cerebrovascular outcomes make comparisons difficult. Comprehensive assessments of cerebrovascular function of the intra- and extracranial arteries to determine the physiological implications of menopause on CBF with healthy ageing is warranted.

Cerebral Autoregulation in Ischemic Stroke: From Pathophysiology to Clinical Concepts

Ischemic stroke (IS) is one of the most impacting diseases in the world. In the last decades, new therapies have been introduced to improve outcomes after IS, most of them aiming for recanalization of the occluded vessel. However, despite this advance, there are still a large number of patients that remain disabled. One interesting possible therapeutic approach would be interventions guided by cerebral hemodynamic parameters such as dynamic cerebral autoregulation (dCA). Supportive hemodynamic therapies aiming to optimize perfusion in the ischemic area could protect the brain and may even extend the therapeutic window for reperfusion therapies. However, the knowledge of how to implement these therapies in the complex pathophysiology of brain ischemia is challenging and still not fully understood. This comprehensive review will focus on the state of the art in this promising area with emphasis on the following aspects: (1) pathophysiology of CA in the ischemic process; (2) methodology used to evaluate CA in IS; (3) CA studies in IS patients; (4) potential non-reperfusion therapies for IS patients based on the CA concept; and (5) the impact of common IS-associated comorbidities and phenotype on CA status. The review also points to the gaps existing in the current research to be further explored in future trials.

Neurobiology of resilience in depression: immune and vascular insights from human and animal studies

Major depressive disorder (MDD) is a chronic and recurrent psychiatric condition characterized by depressed mood, social isolation and anhedonia. It will affect 20% of individuals with considerable economic impacts. Unfortunately, 30-50% of depressed individuals are resistant to current antidepressant treatments. MDD is twice as prevalent in women and associated symptoms are different. Depression's main environmental risk factor is chronic stress, and women report higher levels of stress in daily life. However, not every stressed individual becomes depressed, highlighting the need to identify biological determinants of stress vulnerability but also resilience. Based on a reverse translational approach, rodent models of depression were developed to study the mechanisms underlying susceptibility vs resilience. Indeed, a subpopulation of animals can display coping mechanisms and a set of biological alterations leading to stress resilience. The aetiology of MDD is multifactorial and involves several physiological systems. Exacerbation of endocrine and immune responses from both innate and adaptive systems are observed in depressed individuals and mice exhibiting depression-like behaviours. Increasing attention has been given to neurovascular health since higher prevalence of cardiovascular diseases is found in MDD patients and inflammatory conditions are associated with depression, treatment resistance and relapse. Here, we provide an overview of endocrine, immune and vascular changes associated with stress vulnerability vs. resilience in rodents and when available, in humans. Lack of treatment efficacy suggests that neuron-centric treatments do not address important causal biological factors and better understanding of stress-induced adaptations, including sex differences, could contribute to develop novel therapeutic strategies including personalized medicine approaches.

Integrative cardiovascular control in women: Regulation of blood pressure, body temperature, and cerebrovascular responsiveness

Over the past several decades, it has become increasingly clear that women have distinct cardiovascular profiles compared to men. In this review, our goal is to provide an overview of the literature regarding the influences of female sex and reproductive hormones (primarily estradiol) on mechanisms of cardiovascular control relevant to regulation of blood pressure, body temperature, and cerebral blood flow. Young women tend to have lower resting blood pressure compared with men. This sex difference is reversed at menopause, when women develop higher sympathetic nerve activity and the risk of systemic hypertension increases sharply as postmenopausal women age. Vascular responses to thermal stress, including cutaneous vasodilation and vasoconstriction, are also affected by reproductive hormones in women, where estradiol appears to promote vasodilation and heat dissipation. The influence of reproductive hormones on cerebral blood flow and sex differences in the ability of the cerebral vasculature to increase its blood flow (cerebrovascular reactivity) are relatively new areas of investigation. Sex and hormonal influences on integrative blood flow regulation have further implications during challenges to physiological homeostasis, including exercise. We propose that increasing awareness of these sex-specific mechanisms is important for optimizing health care and promotion of wellness in women across the life span.

Cerebral blood flow regulation in end-stage kidney disease

Patients with chronic kidney disease (CKD) and end-stage kidney disease (ESKD) experience an increased risk of cerebrovascular disease and cognitive dysfunction. Hemodialysis (HD), a major modality of renal replacement therapy in ESKD, can cause rapid changes in blood pressure, osmolality, and acid-base balance that collectively present a unique stress to the cerebral vasculature. This review presents an update regarding cerebral blood flow (CBF) regulation in CKD and ESKD and how the maintenance of cerebral oxygenation may be compromised during HD. Patients with ESKD exhibit decreased cerebral oxygen delivery due to anemia, despite cerebral hyperperfusion at rest. Cerebral oxygenation further declines during HD due to reductions in CBF, and this may induce cerebral ischemia or "stunning." Intradialytic reductions in CBF are driven by decreases in cerebral perfusion pressure that may be partially opposed by bicarbonate shifts during dialysis. Intradialytic reductions in CBF have been related to several variables that are routinely measured in clinical practice including ultrafiltration rate and blood pressure. However, the role of compensatory cerebrovascular regulatory mechanisms during HD remains relatively unexplored. In particular, cerebral autoregulation can oppose reductions in CBF driven by reductions in systemic blood pressure, while cerebrovascular reactivity to CO₂ may attenuate intradialytic reductions in CBF through promoting cerebral vasodilation. However, whether these mechanisms are effective in ESKD and during HD remain relatively unexplored. Important areas for future work include investigating potential alterations in cerebrovascular regulation in CKD and ESKD and how key regulatory mechanisms are engaged and integrated during HD to modulate intradialytic declines in CBF.

Structural and Functional Remodeling of the Brain Vasculature Following Stroke

Maintenance of cerebral blood vessel integrity and regulation of cerebral blood flow ensure proper brain function. The adult human brain represents only a small portion of the body mass, yet about a quarter of the cardiac output is dedicated to energy consumption by brain cells at rest. Due to a low capacity to store energy, brain health is heavily reliant on a steady supply of oxygen and nutrients from the bloodstream, and is thus particularly vulnerable to stroke. Stroke is a leading cause of disability and mortality worldwide. By transiently or permanently limiting tissue perfusion, stroke alters vascular integrity and function, compromising brain homeostasis and leading to widespread consequences from early-onset motor deficits to long-term cognitive decline. While numerous lines of investigation have been undertaken to develop new pharmacological therapies for stroke, only few advances have been made and most clinical trials have failed. Overall, our understanding of the acute and chronic vascular responses to stroke is insufficient, yet a better comprehension of cerebrovascular remodeling following stroke is an essential prerequisite for developing novel therapeutic options. In this review, we present a comprehensive update on post-stroke cerebrovascular remodeling, an important and growing field in neuroscience, by discussing cellular and molecular mechanisms involved, sex differences, limitations of preclinical research design and future directions.

Cerebral Blood Flow Is Reduced in Severe Myalgic Encephalomyelitis/Chronic Fatigue Syndrome Patients During Mild Orthostatic Stress Testing: An Exploratory Study at 20 Degrees of Head-Up Tilt Testing

Introduction: In a study of 429 adults with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), we demonstrated that 86% had symptoms of orthostatic intolerance in daily life. Using extracranial Doppler measurements of the internal carotid and vertebral arteries during a 30-min head-up tilt to 70 degrees, 90% had an abnormal reduction in cerebral blood flow (CBF). A standard head-up tilt test of this duration might not be tolerated by the most severely affected bed-ridden ME/CFS patients. This study examined whether a shorter 15-min test at a lower 20 degree tilt angle would be sufficient to provoke reductions in cerebral blood flow in severe ME/CFS patients. Methods and results: Nineteen severe ME/CFS patients with orthostatic intolerance complaints in daily life were studied: 18 females. The mean (SD) age was 35(14) years, body surface area (BSA) was 1.8(0.2) m² and BMI was 24.0(5.4) kg/m². The median disease duration was 14 (IQR 5–18) years. Heart rate increased, and stroke volume index and end-tidal CO₂ decreased significantly during the test (p ranging from <0.001 to <0.0001). The cardiac index decreased by 26(7)%: p < 0.0001. CBF decreased from 617(72) to 452(63) mL/min, a 27(5)% decline. All 19 severely affected ME/CFS patients met the criteria for an abnormal CBF reduction. Conclusions: Using a less demanding 20 degree tilt test for 15 min in severe ME/CFS patients resulted in a mean CBF decline of 27%. This is comparable to the mean 26% decline previously noted in less severely affected patients studied during a 30-min 70 degree head-up tilt. These observations have implications for the evaluation and treatment of severely affected individuals with ME/CFS.

Aging influences cerebrovascular myogenic reactivity and BK channel function in a sex-specific manner

AIMS

The myogenic reactivity of the middle cerebral arteries (MCA) protects the brain by altering the diameter in response to changes in lumen pressure. Large conductance potassium (BK) channels are known to regulate the myogenic reactivity, yet, it is not clear how aging alters the myogenic reactivity via the BK channel in males and females. Thus, we hypothesize that age-associated changes in BK channel subunits modulate the myogenic reactivity in a sex-specific manner.

METHODS AND RESULTS

We used vascular reactivity, patch-clamp, and biochemical methods to measure myogenic reactivity, BK channel function, and expression, respectively in cerebral vessels of adult and aged male and female Sprague Dawley rats. Our results suggest that aging and ovariectomy (OVX) exaggerated the myogenic reactivity of MCA in females but attenuated it in males. Aging induced outward eutrophic remodelling in females but inward hypertrophic remodelling in males. Aging decreased total, Kv, BK channel currents, and spontaneous transient outward currents (STOC) in vascular smooth muscle cells isolated from females, but not in males. Aging increased BKα subunit mRNA and protein both in males and females. However, aging decreased BKβ1 subunit protein and mRNA in females only. In males, BKβ1 mRNA is increased, but protein is decreased. Iberiotoxin-induced MCA constriction is lower in aged females but higher in aged males. Activation of BKα (10 µM NS1619) and BKβ1 (10 µM S-Equol) subunits failed to increase STOCs and were unable to decrease the myogenic reactivity of MCA in aged female but not in aged male rats. OVX decreased, but chronic supplementation of oestradiol restored BK channel expression and function.

CONCLUSION

Overall our results suggest that aging or OVX-associated downregulation of the BKβ1 expression and function in females results in exaggerated myogenic reactivity of MCA. However, age-associated increase in BK channel function in males attenuated myogenic reactivity of MCA.

Comparable blood velocity changes in middle and posterior cerebral arteries during and following acute high-intensity exercise in young fit women

The cerebral blood flow response to high-intensity interval training (HIIT) remains unclear. HIIT induces surges in mean arterial pressure (MAP), which could be transmitted to the brain, especially early after exercise onset. The aim of this study was to describe regional cerebral blood velocity changes during and following 30 s of high-intensity exercise. Ten women (age: 27 ± 6 years; VO2max : 48.6 ± 3.8 ml·kg·min-1 ) cycled for 30 s at the workload reached at V ˙ O2max followed by 3min of passive recovery. Middle (MCAvmean ) and posterior cerebral artery mean blood velocities (PCAvmean ; transcranial Doppler ultrasound), MAP (finger photoplethysmography), and end-tidal carbon dioxide partial pressure (PET CO2 ; gaz analyzer) were measured. MCAvmean (+19 ± 10%) and PCAvmean (+21 ± 14%) increased early after exercise onset, returning toward baseline values afterward. MAP increased throughout exercise (p < .0001). PET CO2 initially decreased by 3 ± 2 mmHg (p < .0001) before returning to baseline values at end-exercise. During recovery, MCAvmean (+43 ± 15%), PCAvmean (+42 ± 15%), and PET CO2 (+11 ± 3 mmHg; p < .0001) increased. In young fit women, cerebral blood velocity quickly increases at the onset of a 30-s exercise performed at maximal workload, before returning to baseline values through the end of the exercise. During recovery, cerebral blood velocity augments in both arteries, along with PET CO2 .

Cerebrovascular reactivity and cerebral autoregulation are improved in the supine posture compared to upright in healthy men and women

Cerebrovascular reactivity and cerebral autoregulation are two major mechanisms that regulate cerebral blood flow. Both mechanisms are typically assessed in either supine or seated postures, but the effects of body position and sex differences remain unclear. This study examined the effects of body posture (supine vs. seated vs. standing) on cerebrovascular reactivity during hyper and hypocapnia and on cerebral autoregulation during spontaneous and slow-paced breathing in healthy men and women using transcranial Doppler ultrasonography of the middle cerebral artery. Results indicated significantly improved cerebrovascular reactivity in the supine compared with seated and standing postures (supine = 3.45±0.67, seated = 2.72±0.53, standing = 2.91±0.62%/mmHg, P<0.0167). Similarly, cerebral autoregulatory measures showed significant improvement in the supine posture during slow-paced breathing. Transfer function measures of gain significantly decreased and phase significantly increased in the supine posture compared with seated and standing postures (gain: supine = 1.98±0.56, seated = 2.37±0.53, standing = 2.36±0.71%/mmHg; phase: supine = 59.3±21.7, seated = 39.8±12.5, standing = 36.5±9.7°; all P<0.0167). In contrast, body posture had no effect on cerebral autoregulatory measures during spontaneous breathing. Men and women had similar cerebrovascular reactivity and similar cerebral autoregulation during both spontaneous and slow-paced breathing. These data highlight the importance of making comparisons within the same body position to ensure there is not a confounding effect of posture.

Does Gender Influence the Relationship Between High Blood Pressure and Dementia? Highlighting Areas for Further Investigation

BACKGROUND

Gender differences have been noted in studies linking blood pressure to all-cause dementia, and the two most common forms of dementia: Alzheimer's disease (AD) and vascular dementia (VaD). However, how gender modifies the relationship between blood pressure and dementia remains unclear.

OBJECTIVE

To review evidence for a gender modifying effect on the link between blood pressure and all-cause dementia.

METHODS

A systematic review was conducted according to PRISMA guidelines. Sixteen out of 256 reviewed articles met inclusion criteria.

RESULTS

For women, higher midlife systolic blood pressure (SBP) and hypertension were both associated with greater risk of all-cause dementia, AD, and VaD, in six out of seven studies. Two of these studies reported higher midlife SBP/hypertension were associated with greater risk for all-cause dementia in women, but not men. One study reported higher midlife SBP associated with greater AD risk in women, but not men. However, another study reported that midlife hypertension associated with AD risk in men, but not women. No clear gender differences were reported in the relationship between late-life high blood pressure/hypertension with all-cause dementia or AD.

CONCLUSION

Studies rarely, and inconsistently, analyzed or reported gender effects. Therefore, interpretation of available evidence regarding the role of gender in blood pressure associated dementia was difficult. Several studies indicated higher midlife SBP was associated with greater risk of all-cause dementia for women, compared to men. Future studies should evaluate women-specific aging processes that occur in midlife when considering the association between blood pressure and dementia risk.

Can we assess dynamic cerebral autoregulation in stroke patients with high rates of cardiac ectopicity?

It is unclear whether physiological recordings containing high numbers of ectopic heartbeats can be used to measure the cerebral autoregulation (CA) of blood flow. This study evaluated the utility of such data for assessing dynamic CA capacity. Physiological recordings of cerebral blood flow velocity, heart rate, end-tidal CO₂ and beat-to-beat blood pressure from acute ischaemic stroke (AIS) patients (n = 46) containing ectopic heartbeats of varying number (0.2 to 25 occurrences per minute) were analysed. Dynamic CA was determined using the autoregulation index (ARI) and the normalised mean square error (NMSE) was used to evaluate the fitting of the step response between BP and CBFV to Tiecks' model. We fitted linear mixed models on the CA variables incorporating ectopic burden, age, sex and hemisphere as predictor variables. Ectopic activity demonstrated an association with mean coherence (p = 0.006) but not with ARI (p = 0.162), impaired CA based on dichotomised ARI (p = 0.859) or NMSE (p = 0.671). Dynamic CA could be reliably assessed in AIS patients using physiological recordings with high rates of cardiac ectopic activity. This provides supportive data for future studies evaluating CA capability in AIS patients, with the potential to develop more individualised treatment strategies. Graphical Abstract.

Sex differences in cerebral autoregulation are unaffected by menstrual cycle phase in young, healthy women

Sex is known to affect the prevalence of conditions such as stroke. However, effects of sex on cerebral blood flow regulation are still not well understood. Critical to this understanding is how fluctuations in hormones across the menstrual cycle affect cerebral autoregulation. We measured autoregulation in the early follicular, late follicular, and midluteal phases during spontaneous and induced blood pressure oscillations in 26 young, healthy individuals (13 women and 13 men, age: 26 ± 4 yr). Men participated three times, ~1–3 wk apart. Beat-by-beat blood pressure, heart rate, end-tidal CO2, and transcranial Doppler ultrasonography of the middle (MCA) and anterior (ACA) cerebral arteries were obtained. We did not find a difference in cerebral autoregulation across the menstrual cycle in women but found significantly improved autoregulation in the MCA and ACA of women compared with men. Women demonstrated significantly lower MCA gain (0.97 ± 0.13 vs. 1.17 ± 0.14%/mmHg, P = 0.001), higher MCA phase (46.1 ± 12.6 vs. 35.8 ± 7.9°, P = 0.019), and higher ACA phase (40.5 ± 10.8 vs 31.5 ± 8.5°, P = 0.040) during repeated squat-to-stand maneuvers. Women also had lower MCA gain (1.50 ± 0.11 vs. 1.72 ± 0.30%/mmHg, P = 0.029) during spontaneous fluctuations in pressure while standing and less of a decrease in MCA flow velocity (−18.7 ± 2.7 vs. −23.2 ± 6.0%, P = 0.014) during sit-to-stand maneuvers. Our results suggest that young women have improved cerebral autoregulation compared with young men regardless of menstrual cycle phase and that autoregulation is relatively robust to acute fluctuations in female sex hormones.

NEW & NOTEWORTHY This is the first study to investigate thoroughly the effects of menstrual cycle phase and sex differences in cerebral autoregulation in young, healthy individuals. Cerebral autoregulation was unaffected by menstrual cycle phase during both repeated squat-to-stand and sit-to-stand maneuvers. However, women demonstrated significantly improved cerebral autoregulation in the middle and anterior cerebral arteries, suggesting women were able to maintain cerebral blood flow during changes in blood pressure more efficiently than men.

Sex differences in the ventilatory and cardiovascular response to supine and tilted metaboreflex activation

Women have attenuated exercise pressor responses compared to men; however, their cerebrovascular and ventilatory responses have not been previously measured. Furthermore, recent evidence has shown that posture change can influence the response of the metaboreflex but this has only been tested in men. Young and healthy men (n = 14; age: 21 ± 2) and women (n = 11; age: 19 ± 1) underwent 40% MVC static handgrip exercise (HG) for 2 min followed by 3 min of post-exercise circulatory occlusion (PECO) in the supine and 70° tilted postures. In supine position during HG and PECO only men had an increase in ventilation (Men: Baseline: 12.5 ± 1.7 L/min, HG: 18.6 ± 5.3 L/min, PECO: 17.7 ± 10.3 L/min; Women: Baseline: 12.0 ± 1.5 L/min, HG: 12.4 ± 1.2 L/min, PECO: 11.5 ± 1.3 L/min; Sex × Time interaction P = 0.037). In supine position during HG and PECO men and women had similar reductions in cerebrovascular conductance (Men: Baseline: 0.79 ± 0.13 cm/sec/mmHg, HG: 0.68 ± 0.18 cm/sec/mmHg, PECO: 0.61 ± 0.19 cm/s/mmHg; Women: Baseline: 0.87 ± 0.13 cm/sec/mmHg, HG: 0.83 ± 0.14 cm/sec/mmHg, PECO: 0.75 ± 0.17 cm/sec/mmHg; P < 0.015 HG/PECO vs. baseline). When comparing the response to PECO in the supine versus upright postures there was a significant attenuation in the increase in mean arterial pressure in both men and women (Supine posture: Men: +23.3 ± 14.5 mmHg, Women: +12.0 ± 7.3 mmHg; Upright posture: Men: +15.7 ± 14.1 mmHg, Women: +7.7 ± 6.7 mmHg; Main effect of sex P = 0.042, Main effect of posture P < 0.001). Our results indicate sexually dimorphic ventilatory responses to HG and PECO which could be due to different interactions of the metaboreflex and chemoreflex. We have also shown evidence of attenuated metaboreflex function in the upright posture in both men and women.

Health and Functional Determinants of Orthostatic Hypotension in Geriatric Ward Patients: A Retrospective Cross Sectional Cohort Study

OBJECTIVE

Orthostatic hypotension (OH) is a common problem in older people. Although it is indicated that OH can be a marker of frailty there are no studies that evaluate this relationship in hospitalized patients. The aim of the study was to assess the prevalence of OH in geriatric ward patients and its association with health and functional ability characteristics and patients' frailty status.

DESIGN AND SETTING

A retrospective cross-sectional cohort study was conducted among patients aged 60 or over hospitalized in the geriatric ward.

PARTICIPANTS

Patients' medical records were analyzed and those with Active Standing Test (AST) results were included in the study.

MEASUREMENTS

Orthostatic hypotension was defined by a drop in blood pressure of at least 20mmHg for systolic blood pressure and at least 10mmHg for diastolic blood pressure within 3minutes of standing up in AST. The database included sociodemographic characteristics, nutritional, functional and cognitive state, comorbidity and medical treatment. Frailty syndrome was diagnosed with Clinical Frailty Scale. Correlations with OH were counted and multivariable logistic regression models were built.

RESULTS

416 patients were hospitalized in the study period and 353 (84.9%) were included, 78 (22.1%) men and 298 (84.4%) 75+ year-old. AST was not available in patients significantly more dependent in ADL and more frail. OH was diagnosed in 57 (16.2%) patients, significantly more frequently in men (systolic- 45,5%, systolic-diastolic- 40,0%). The significant independent predictors of OH were lower diastolic blood pressure at admittance, nutritional risk in MNA-SF, Parkinson disease, α1-blockers, neuroleptics and memantine, and not the frailty syndrome diagnosed with Clinical Frailty Scale.

CONCLUSIONS

OH affects a significant percentage of patients in the geriatric ward, although this problem may be underestimated due to limitations in the performance of AST in very frail and functionally dependent patients.

Dynamic cerebral autoregulation is attenuated in young fit women

Young women exhibit higher prevalence of orthostatic hypotension with presyncopal symptoms compared to men. These symptoms could be influenced by an attenuated ability of the cerebrovasculature to respond to rapid blood pressure (BP) changes [dynamic cerebral autoregulation (dCA)]. The influence of sex on dCA remains unclear. dCA in 11 fit women (25 ± 2 years) and 11 age-matched men (24 ± 1 years) was compared using a multimodal approach including a sit-to-stand (STS) and forced BP oscillations (repeated squat-stand performed at 0.05 and 0.10 Hz). Prevalence of initial orthostatic hypotension (IOH; decrease in systolic ≥ 40 mmHg and/or diastolic BP ≥ 20 mmHg) during the first 15 sec of STS was determined as a functional outcome. In women, the decrease in mean middle cerebral artery blood velocity (MCAvmean ) following the STS was greater (-20 ± 8 vs. -11 ± 7 cm sec-1 ; P = 0.018) and the onset of the regulatory change (time lapse between the beginning of the STS and the increase in the conductance index (MCAvmean /mean arterial pressure) was delayed (P = 0.007). Transfer function analysis gain during 0.05 Hz squat-stand was ~48% higher in women (6.4 ± 1.3 vs. 3.8 ± 2.3 cm sec-1 mmHg-1 ; P = 0.017). Prevalence of IOH was comparable between groups (women: 4/9 vs. men: 5/9, P = 0.637). These results indicate the cerebrovasculature of fit women has an attenuated ability to react to rapid changes in BP in the face of preserved orthostasis, which could be related to higher resting cerebral blood flow allowing women to better face transient hypotension.

Contributions of sex to cerebrovascular function and pathology

Sex differences exist in how cerebral blood vessels function under both physiological and pathological conditions, contributing to observed sex differences in risk and outcomes of cerebrovascular diseases (CBVDs), such as vascular contributions to cognitive impairment and dementia (VCID) and stroke. Throughout most of the lifespan, women are protected from CBVDs; however, risk increases following menopause, suggesting sex hormones may play a significant role in this protection. The cerebrovasculature is a target for sex hormones, including estrogens, progestins, and androgens, where they can influence numerous vascular functions and pathologies. While there is a plethora of information on estrogen, the effects of progestins and androgens on the cerebrovasculature are less well-defined. Estrogen decreases cerebral tone and increases cerebral blood flow, while androgens increase tone. Both estrogens and androgens enhance angiogenesis/cerebrovascular remodeling. While both estrogens and androgens attenuate cerebrovascular inflammation, pro-inflammatory effects of androgens under physiological conditions have also been demonstrated. Sex hormones exert additional neuroprotective effects by attenuating oxidative stress and maintaining integrity and function of the blood brain barrier. Most animal studies utilize young, healthy, gonadectomized animals, which do not mimic the clinical conditions of aging individuals likely to get CBVDs. This is also concerning, as sex hormones appear to mediate cerebrovascular function differently based on age and disease state (e.g. metabolic syndrome). Through this review, we hope to inspire others to consider sex as a key biological variable in cerebrovascular research, as greater understanding of sex differences in cerebrovascular function will assist in developing personalized approaches to prevent and treat CBVDs.

Sex differences in cerebral haemodynamics across the physiological range of PaCO2

OBJECTIVE

Cerebral blood flow (CBF) is influenced by changes in arterial CO₂ (PaCO₂). Recently, cerebral haemodynamic parameters were demonstrated to follow a four parameter logistic curve offering simultaneous assessment of dCA and CO₂ vasoreactivity. However, the effects of sex on cerebral haemodynamics have yet to be described over a wide range of PaCO₂.

APPROACH

CBF velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer) and end-tidal CO₂ (EtCO₂, capnography) were measured in healthy volunteers at baseline, and in response to hypo- (-5 mmHg and  -10 mmHg below baseline) and hypercapnia (5% and 8% CO₂), applied in random order.

MAIN RESULTS

Forty-five subjects (19 male, 26 female, mean age 37.5 years) showed significant differences between males and females in CBFV (50.9  ±  10.4 versus 61.5  ±  12.3 cm · s^-1, p  =  0.004), EtCO₂ (39.2  ±  2.8 versus 36.9  ±  3.0 mmHg, p  =  0.005), RAP (1.16  ±  0.23 versus 0.94  ±  0.40 mmHg cm · s^-1, p  =  0.005) and systolic BP (125.2  ±  8.0 versus 114.6  ±  12.4 mmHg, p  =  0.0372), respectively. Significant differences between sexes were observed in the four logistic parameters: y _min, y _max, k (exponential coefficient) and x (EtCO₂ level) across the haemodynamic variables. Significant differences included the CBFV-EtCO₂ and ARI-EtCO₂ relationship; ARI_min (p  =  0.036) and CBFV_max (p  =  0.001), respectively. Furthermore, significant differences were observed for both CrCP_min (p  =  0.045) and CrCP_max (p  =  0.005) and RAP_min (p  <  0.001) and RAP_max (p  <  0.001).

SIGNIFICANCE

This is the first study to examine sex individually within the context of a multi-level CO₂ protocol. The demonstration that the logistic curve parameters are influenced by sex, highlights the need to take into account sex differences between participants in both physiological and clinical studies.

Cerebral Autoregulation in Neonates With and Without Congenital Heart Disease

BACKGROUND

Congenital heart disease (CHD) is a leading birth defect in the United States, affecting about 40 000 neonates each year. Despite efforts to prevent developmental delays, many children with CHD have neurological deficits that last into adulthood, influencing employability, self-care, and quality of life.

OBJECTIVE

To determine if neonates with CHD have impaired cerebral autoregulation and poorer neurodevelopmental outcomes compared with healthy controls.

METHODS

A total of 44 full-term neonates, 28 with CHD and 16 without, were enrolled in the study. Inclusion criteria included confirmed diagnosis of CHD, stable hemodynamic status, and being no more than 12 days old. Exclusion criteria included intraventricular hemorrhage and intubation. Cerebral autoregulation was determined by measuring regional cerebral oxygenation during a postural change. The Einstein Neonatal Neurobehavioral Assessment Scale was used to measure overall neurodevelopmental outcomes (motor, visual, and auditory functions).

RESULTS

Of the 28 neonates with CHD, 8 had single-ventricle physiology. A χ² analysis indicated no significant difference in impaired cerebral autoregulation between neonates with CHD and controls (P = .38). Neonates with CHD had lower regional cerebral oxygenation than did neonates without CHD (P < .001). Regression analyses with adjustments for cerebral autoregulation indicated that neonates with CHD had poorer total neurodevelopmental outcomes scores (β = 9.3; P = .02) and motor scores (β = 7.6; P = .04).

CONCLUSION

Preoperative neonates with CHD have poorer developmental outcomes and more hypoxemia than do controls.

Dynamic Regulation of Cerebral Blood Flow in Patients With Alzheimer Disease

Cerebral autoregulation and baroreflex sensitivity are key mechanisms that maintain cerebral blood flow. This study assessed whether these control mechanisms are affected in patients with dementia and mild cognitive impairment due to Alzheimer disease, as this would increase the risks of antihypertensive treatment. We studied 53 patients with dementia (73.1 years [95% confidence interval (CI), 71.4–74.8]), 37 patients with mild cognitive impairment (69.2 years [95% CI, 66.4–72.0]), and 47 controls (69.4 years [95% CI, 68.3–70.5]). Beat-to-beat blood pressure (photoplethysmography), heart rate, and cerebral blood flow velocity (transcranial Doppler) were measured during 5-minute rest (sitting) and 5 minutes of orthostatic challenges, using repeated sit-to-stand maneuvers. Cerebral autoregulation was assessed using transfer function analysis and the autoregulatory index. Baroreflex sensitivity was estimated with transfer function analysis and by calculating the heart rate response to blood pressure changes during the orthostatic challenges. Dementia patients had the lowest cerebral blood flow velocity ( P =0.004). During rest, neither transfer function analysis nor the autoregulatory index indicated impairments in cerebral autoregulation. During the orthostatic challenges, higher autoregulatory index ( P =0.011) and lower transfer function gain ( P =0.017), indicating better cerebral autoregulation, were found in dementia (4.56 arb. unit [95% CI, 4.14–4.97]; 0.59 cm/s per mm Hg [95% CI, 0.51–0.66]) and mild cognitive impairment (4.59 arb. unit [95% CI, 4.04–5.13]; 0.51 cm/s per mm Hg [95% CI, 0.44–0.59]) compared with controls (3.71 arb. unit [95% CI, 3.35–4.07]; 0.67 cm/s per mm Hg [95% CI, 0.59–0.74]). Baroreflex sensitivity measures did not differ between groups. In conclusion, the key mechanisms to control blood pressure and cerebral blood flow are not reduced in 2 stages of Alzheimer disease compared with controls, both in rest and during orthostatic changes that reflect daily life challenges.

Dynamic cerebral autoregulation is impaired during submaximal isometric handgrip in patients with heart failure

The incidence of neurological complications, including stroke and cognitive dysfunction, is elevated in patients with heart failure (HF) with reduced ejection fraction. We hypothesized that the cerebrovascular response to isometric handgrip (iHG) is altered in patients with HF. Adults with HF and healthy volunteers were included. Cerebral blood velocity (CBV; transcranial Doppler, middle cerebral artery) and arterial blood pressure (BP; Finometer) were continuously recorded supine for 6 min, corresponding to 1 min of baseline and 3 min of iHG exercise, at 30% maximum voluntary contraction, followed by 2 min of recovery. The resistance-area product was calculated from the instantaneous BP-CBV relationship. Dynamic cerebral autoregulation (dCA) was assessed with the time-varying autoregulation index estimated from the CBV step response derived by an autoregressive moving-average time-domain model. Forty patients with HF and 23 BP-matched healthy volunteers were studied. Median left ventricular ejection fraction was 38.5% (interquartile range: 0.075%) in the HF group. Compared with control subjects, patients with HF exhibited lower time-varying autoregulation index during iHG, indicating impaired dCA ( P < 0.025). During iHG, there were steep rises in CBV, BP, and heart rate in control subjects but with different temporal patterns in HF, which, together with the temporal evolution of resistance-area product, confirmed the disturbance in dCA in HF. Patients with HF were more likely to have impaired dCA during iHG compared with age-matched control subjects. Our results also suggest an impairment of myogenic, neurogenic, and metabolic control mechanisms in HF. The relationship between impaired dCA and neurological complications in patients with HF during exercise deserves further investigation. NEW & NOTEWORTHY Our findings provide the first direct evidence that cerebral blood flow regulatory mechanisms can be affected in patients with heart failure during isometric handgrip exercise. As a consequence, eventual blood pressure modulations are buffered less efficiently and metabolic demands may not be met during common daily activities. These deficits in cerebral autoregulation are compounded by limitations of the systemic response to isometric exercise, suggesting that patients with heart failure may be at greater risk for cerebral events during exercise.

Cerebrovascular Hemodynamics in Women

Sex and gender, as biological and social factors, significantly influence health outcomes. Among the biological factors, sex differences in vascular physiology may be one specific mechanism contributing to the observed differences in clinical presentation, response to treatment, and clinical outcomes in several vascular disorders. This review focuses on the cerebrovascular bed and summarizes the existing literature on sex differences in cerebrovascular hemodynamics to highlight the knowledge deficit that exists in this domain. The available evidence is used to generate mechanistically plausible and testable hypotheses to underscore the unmet need in understanding sex-specific mechanisms as targets for more effective therapeutic and preventive strategies.

Lack of linear correlation between dynamic and steady-state cerebral autoregulation

Key points

For correct application and interpretation of cerebral autoregulation (CA) measurements in research and in clinical care, it is essential to understand differences and similarities between dynamic and steady‐state CA.

The present study found no correlation between dynamic and steady‐state CA indices in healthy older adults.

There was variability between individuals in all (steady‐state and dynamic) autoregulatory indices, ranging from low (almost absent) to highly efficient CA in this healthy population.

These findings challenge the assumption that assessment of a single CA parameter or a single set of parameters can be generalized to overall CA functioning. Therefore, depending on specific research purposes, the choice for either steady‐state or dynamic measures or both should be weighed carefully.

Abstract

The present study aimed to investigate the relationship between dynamic (dCA) and steady‐state cerebral autoregulation (sCA). In 28 healthy older adults, sCA was quantified by a linear regression slope of proportionate (%) changes in cerebrovascular resistance (CVR) in response to proportionate (%) changes in mean blood pressure (BP) induced by stepwise sodium nitroprusside (SNP) and phenylephrine (PhE) infusion. Cerebral blood flow (CBF) was measured at the internal carotid artery (ICA) and vertebral artery (VA) and CBF velocity at the middle cerebral artery (MCA). With CVR = BP/CBF, Slope‐CVR_ICA, Slope‐CVR_VA and Slope‐CVRi_MCA were derived. dCA was assessed (i) in supine rest, analysed with transfer function analysis (gain and phase) and autoregulatory index (ARI) fit from spontaneous oscillations (ARI_Baseline), and (ii) with transient changes in BP using a bolus injection of SNP (ARI_SNP) and PhE (ARI_PhE). Comparison of sCA and dCA parameters (using Pearson's r for continuous and Spearman's ρ for ordinal parameters) demonstrated a lack of linear correlations between sCA and dCA measures. However, comparisons of parameters within dCA and within sCA were correlated. For sCA slope‐CVR_VA with Slope‐CVRi_MCA (r = 0.45, P < 0.03); for dCA ARI_SNP with ARI_PhE (ρ = 0.50, P = 0.03), ARI_Baseline (ρ = 0.57, P = 0.03) and Phase_LF (ρ = 0.48, P = 0.03); and for Gain_VLF with Gain_LF (r = 0.51, P = 0.01). By contrast to the commonly held assumption based on an earlier study, there were no linear correlations between sCA and dCA. As an additional observation, there was strong inter‐individual variability, both in dCA and sCA, in this healthy group of elderly, in a range from low to high CA efficiency.

For correct application and interpretation of cerebral autoregulation (CA) measurements in research and in clinical care, it is essential to understand differences and similarities between dynamic and steady‐state CA.

The present study found no correlation between dynamic and steady‐state CA indices in healthy older adults.

There was variability between individuals in all (steady‐state and dynamic) autoregulatory indices, ranging from low (almost absent) to highly efficient CA in this healthy population.

These findings challenge the assumption that assessment of a single CA parameter or a single set of parameters can be generalized to overall CA functioning. Therefore, depending on specific research purposes, the choice for either steady‐state or dynamic measures or both should be weighed carefully.

Influence of sex, menstrual cycle, and oral contraceptives on cerebrovascular resistance and cardiorespiratory function during Valsalva or standing

Women experience orthostatic intolerance more than men, and they experience faintness more in the early follicular [i.e., low-hormone (LH)] than luteal [i.e., high-hormone (HH)] phase of the menstrual cycle. Men (n = 13, 25.8 ± 1.8 yr old) and women in the LH (days 2-5; placebo) and HH (days 18-24; high dose) phases of the menstrual cycle with (OC; n = 14, 22.0 ± 0.8 yr old) or without (NOC; n = 12, 21.8 ± 0.5 yr old) oral contraceptive (OC) use underwent the Valsalva maneuver and a supine-sit-stand protocol. Blood pressure, normalized stroke volume [stroke volume index (SVi)], cardiac output index, heart rate, end-tidal CO₂, and middle cerebral artery (MCA) blood flow velocity were measured. When subjected to the Valsalva maneuver, all women had a greater increase in diastolic and mean MCA blood flow velocity than men (P ≤ 0.065), with no significant effect of menstrual cycle phase or OC use. When subjected to the supine-sit-stand protocol, men had lower MCA blood flow velocity (P < 0.038) than all women, and SVi was higher in men than in the NOC group in all postures (P < 0.011) and in the OC group in the LH phase of the menstrual cycle during standing (P = 0.010). Only men experienced higher resistance index (P < 0.001) and pulsatility index (P < 0.001) with standing. The OC group had lower end-tidal CO₂ (P = 0.002) than the NOC group (P = 0.030) and men (P ≤ 0.067). SVi (P = 0.004) and cardiac output index (P = 0.008) were higher in the OC than NOC group. A tendency toward a lower mean MCA blood flow velocity (P = 0.058) and higher SVi (P = 0.059) and pulsatility index (P = 0.058) was noted in the HH than LH phase. Mean arterial pressure was higher in the OC than NOC group in the LH phase (P = 0.049) and lower in the HH than LH phase (P = 0.014). Our results indicate that cycling estrogens/progestins can influence ventilatory, cardiovascular, and/or cerebrovascular physiology.NEW & NOTEWORTHY We have found sex differences in the cerebrovascular response to the Valsalva maneuver and standing. Men have greater cerebral vasoconstriction (or women have greater cerebral vasodilation) during late phase II of the Valsalva maneuver, and the cerebrovascular resistance index increases in men, but not in women, during standing. Furthermore, our findings indicate that both the menstrual cycle phase and oral contraceptive use can influence cardiovascular function both at rest and during active standing.

Sub-clinical orthostatic hypotension is associated with greater subjective memory impairment in older adults

INTRODUCTION

Orthostatic blood pressure (BP) is a measure of cardiovascular autonomic function. Orthostatic BP dysregulation may lie on the causal pathway to dementia. Subjective memory impairment (SMI) is commonly reported by older people some of whom may progress to dementia. We hypothesised that sub-clinical orthostatic hypotension would be associated with SMI and explored these associations according to sex.

METHODS

Cross-sectional analysis of data from 4340 participants aged 50 and over collected during the first wave (2009-2011) of the cohort study, The Irish Longitudinal Study on Ageing. Subjective memory was rated according to a 5-point scale ranging from 'poor' to 'excellent'. BP was measured during orthostatic stress using continuous non-invasive beat-to-beat recording over 2 min.

RESULTS

2% reported 'poor' subjective memory, 12.3% 'fair' , 38% 'good', 33% 'very good' and 14.6% 'excellent'. After controlling for several potential confounding factors including cardiovascular risk, objective cognition, and depressive symptoms mean systolic orthostatic BP was lowest in those with poor subjective memory: 92.2 mmHg (CI95% = 87.1, 97.3) versus excellent 99.3 mmHg (CI95% = 97.4, 101.2); p = 0.011. Further adjustment for supine systolic BP suggested that men with poor subjective memory reached the lowest average systolic orthostatic BP and had the greatest impairment in systolic orthostatic BP stabilisation to baseline levels at 10 s post-stand (-6.64 mmHg; CI95% = -11.49, -1.79; p = 0.007).

CONCLUSIONS

Sub-clinical orthostatic hypotension is associated with SMI, and there are sex-specific relationships evident in this population-based cohort. Subtle cardiovascular autonomic dysfunction may represent a modifiable risk marker at an early stage of cognitive decline in older adults. Copyright © 2016 John Wiley & Sons, Ltd.